1. Field of the Invention
This invention relates to olefinically unsaturated adducts of propylene with polyunsaturated C.sub.18-22 fatty acids or esters thereof with C.sub.1-36 alkanols in molar ratios of propylene to the fatty acids or fatty acid esters of 1:1 to 2:1 obtainable by reaction of the fatty acids or fatty acid esters with propylene at elevated temperature and elevated pressure in the presence of compounds of transition metals from the group consisting of Ru, Rh, Pd, Ir and Pt as catalysts.
2. Statement of Related Art
Fatty acids branched in the alkyl chain of the Guerbet acid type, obtainable by "guerbetization" of the corresponding fatty alcohols and oxidation of the Guerbet alcohols to the corresponding acids, are technologically interesting intermediate products because they, or their alkyl esters, have distinctly reduced pour points by comparison with the corresponding unbranched isomers. However, the production of Guerbet acids is technologically complicated and can only be carried out with unsatisfactory yields. Accordingly, there has been no shortage of attempts to produce corresponding fatty acid derivatives branched in the alkyl chain from fatty acids or esters thereof. A typical example of this is the layer-silicate-catalyzed dimerization of fatty acids. Unfortunately, considerable quantities of trimeric fatty acids and methyl-branched fatty acids, so-called isofatty acids, are also formed in this reaction. Another, albeit complicated, process gives branched fatty acid derivatives from conjuene fatty acids in the trans-trans form with activated dienophiles under the conditions of a Diels-Alder reaction; for example, a branched C.sub.21 dicarboxylic acid can be obtained in this way from linoleic acid and acrylic acid, of cf. U.S. Pat. No. 3,734,859, U.S. Pat. No. 3,753,968, DE-B 2 253 930. Other branched fatty acid derivatives have been obtained by thermal or acid-catalyzed addition of activated enophiles onto unsaturated fatty acid derivatives. For example, maleic anhydride can be added onto oleic acid in the presence of an acid as catalyst in yields of up to 70%, cf. Fat. Sci. Technol., 1, 1 (1988). However, the presence of more than one carboxyl group in the reaction products mentioned above has often proved to be troublesome.
Finally, attempts have also been made to add saturated hydrocarbons onto fatty acids by heat-initiated radical addition of saturated hydrocarbons onto fatty acids. The addition of cyclohexane onto oleic acid methyl ester at 340.degree. C./200 bar gives alkyl-branched fatty acids with 70% selectivity, but in a yield of only 2.8%, cf. J. O. Metzger et al., Fat. Sci. Technol. 1 (1989), 18.